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Funcionalización estéricamente dirigida de enlaces aromáticos C-H: borilación selectiva de orto a ciano grupos en

Ghayoor A Chotana¹, Michael A Rak, Milton R Smith

¹Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.

Journal of the American Chemical Society

|July 28, 2005

Resumen

Este estudio introduce la borilación catalizada por iridio para la funcionalización de los benzonitriles en la posición 2, ofreciendo una nueva ruta para la activación de C-H. El método también se extiende a los heterociclos, lo que permite la diborilación selectiva en casos específicos.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis es la catálisis.
Síntesis orgánica La síntesis orgánica.

Sus antecedentes:

Los métodos tradicionales como la sustitución aromática electrofílica y la orto-metalización dirigida tienen limitaciones en la regioselectividad para ciertos sustratos.
El grupo ciano en los benzonitriles presenta desafíos únicos para la funcionalización directa.
La activación de C-H ofrece una poderosa estrategia para la funcionalización directa de compuestos aromáticos y heteroaromáticos.

Objetivo del estudio:

Desarrollar un nuevo método de activación/borilación de C-H catalizado por iridio para los benzonitriles 4-sustituidos.
Para lograr la funcionalización regioselectiva en la posición 2, adyacente al grupo ciano.
Explorar la extensión de esta metodología a los heterociclos ciano-sustituidos e investigar la diborilación.

Principales métodos:

Reacciones de borilación catalizadas por iridio utilizando varios reactivos de boro.
Variación sistemática de 4-sustitutos en los benzonitriles para estudiar los efectos estéricos.
Aplicación del método desarrollado a heterociclos ciano-sustituidos de cinco y seis miembros.

Principales resultados:

La borilación regioselectiva exitosa de C-H en la posición 2 de los benzonitriles 4-sustituidos, particularmente cuando el 4-sustituto es estéricamente exigente.
Demostración de la diborilación bajo condiciones específicas, dando como resultado un único regioisómero.
Extensión de la estrategia de borilación estéricamente dirigida a varios sistemas heterocíclicos sustituidos por ciano.

Conclusiones:

La borilación C-H catalizada por iridio proporciona un método complementario y eficaz para la funcionalización de los benzonitriles, superando las limitaciones de los enfoques tradicionales.
El control estérico es un factor clave para lograr la regioselectividad en la posición 2.
La metodología es versátil y aplicable a una serie de importantes andamios heterocíclicos.

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